Telescopic hydraulic shock absorber



R. SMITH TELESCOPIC HYDRAULIC SHOCK ABSORBER March 23, 1954 3Sheets-Sheet l Filed Nov. 14, 1949 I J zw# W. er r mm m M 9m om@ 2U imFl. Wl

R. SMITH TELESCOPIC HYDRAULIC SHOCK ABSORBER March 23, 1954 5Sheets-Sheet 2 Filed NOV. 14, 1949 Ro/v/MD 5mm March 23, 1954 R SMITH2,672,952

TELESCOPIC HYDRAULIC SHOCK BSORBER Filed NOV. 14, 1949 5 Sheets-Sheet 311u/calor;

,gon/up SMITH Patented Mar. 23, 1954 TELESCOPIC HYDRAULIC SHOCK ABSORBERRonald Smith, Eastgate, Beverley, England, assignor to ArmstrongsPatents Company Limited, Eastgate, Beverley, England, a British companyApplicationNovexnber 14, 1949, Serial No. 126,943

Claims'priority, application Great Britain November 20, 1948 (Cl.18S-88) 2 Claims.

'I'his invention concerns vhydraulic shock absorbers of the so-calledtelescopic type, that is to say of the type wherein an attachment pointfor connection to one part of a, vehicle is xed to a piston and a secondattachment point for connection to another part ofthe vehicle is fixedto a complementary cylinder so that control of relative movementfbetween said parts vof the vehicle may be eiected in a, direction axialof said piston and of said cylinder.

An object of, this invention is to provide an hydraulic telescopic shockabsorber of simple construction which may be produced at a relativelylow cost.

According to the present invention a telescopic hydraulic shock absorbercomprises, in combination, a pressure cylinder, a piston displaceableaxially within said pressure cylinder, a liquid reservoir disposedexternally to said pressure cylinder, two similarly directed non-returnvalves, one of which is a piston valve arranged to reciprocate within acounter bore in the connecting rod of the piston and the other of whichis located at the bottom of the pressure cylinder, a bleed path from thecounter bore in the piston rod to the interior of the pressure cylinderthereby oscillations of the valve in the piston are dampedhydraulically, a passage extending between the top of the pressureycylinder and the top of the liquid reservoir, a dependent liquiddischarge pipe extending from said passage to beneath the level ofliquid in the reservoir, and 'a non-return Valve assembly located at thelower end of the liquid discharge pipe and comprising a cylindricalelement and a piston'valve adapted to reciprocate within saidcylindrical element and a bleed path located beneath said cylindricalele-l ment whereby oscillations of the said last named piston valve aredamped hydraulically.

'I'he invention will be described further by way of example withreference to the accompanying drawings, in which:

Fig. 1 is a vertical section, y

Fig. 2 is a detail in vertical section on an enlarged scale showing theconstruction of the lower portion of the depending liquid discharge pipeillustrated in Fig. 1,

Fig. 3 is a view similar to that of Fig. 2 ybut illustrating a modifiedvalve arrangement at the lower end of the liquid discharge pipe, and

Fig. 4 is a fragmentary vertical section 'of a telescopic shock'absorber showing a. modied valve arrangement at the lower end of theliquiddis'charge pipefand between upper and lower parts of the pressurecy1inder,` and 'by the ac'- companying drawingsin which: v

Fig. 5 is a vertical section,

Fig. 6 is a cross section on the line VI-VI of Fig. 5 of a modifiedtelescopic shock absorber, and

Fig. 7 is a detail in vertical section on an enlarged scale showing theconstruction of a modied valve assembly' at the lower end of thedepending liquid discharge pipe.

Fig. 8 is a detail on an enlarged scale of the piston valve assemblyshown in Fig. 4.

Fig. 9 is a detail on an enlarged scale of the piston valve assemblyshown in Fig. 5.

A telescopic shock absorber (Fig. 1) includes a piston fixed to aconnecting rod I2. The piston is displaceable in a pressure cylinder |4.The lower end ofthe cylinder I4 is closed by a base 21 includinga'spring steel valve disc 28, slidably mounted on a rivet 29 secured inan axial bore in the basev 2'I, which acts as a Valve body.

The upper end of 'the cylinder I4 is xed to a cylinder head 2|, which inturn is secured within, so as to close, the upper end of a tube 20surrounding the cylinder" I4. The cylinder and tube are sol assembled4that the base 21 is urged into contact with the closed lower end of thetube 20. Secured las by welding to the lower end of the tube 2D is adepending bolt 32, adapted to connect the tube 20 to a vehicle portion3| by way of two rubber blocks 34 and 35. The upper end of theconnectingrod I2 is attached by way of a dished end 23 to a bolt 42,which is similarly attached to another vehicle portion 4| by way ofrubber`blocks-44 and 45. A dust excluding cover 24 `of 'tubular shape isattached, preferably by soft solder or spot welding to the anged portionof the end 23.

The piston II includes a non-return valve assembly incorporating alvalve I6. The cylinder head 2| is axially bored to allow passagetherethrough of the connecting rod I2, which is sealed, preferably,asshown, by aA washer or ring 22 located in a circumferential rebate inthe wall of the axial bore, orby anyother convenient sealing means. t

The cylinder head 2| includes'an undercut groove, which Vis co-axialrelative to the main bore, and said groove communicates by way of anoblique narrow vbore 2|a with an annular reservoir provided between theexterior of the cylinder I4 and the interior of the tube 20. Thisundercut groove and oblique bore is forrthe purposeotfdraining fluidwhich has leaked ,between the connectingrod I2 and the main "axial borein the cylinder head. There isfalso-.fanpblique bore 2|t providingcommunication between the interior of the upper end of the cylinder I4and a bore 21u within which is threadedly engaged an upper reduced endr`portion ofizaidependingi liquid discharge pipe"26. The-lower--endportionof the pipe 26 is constricted at 26a (Figs. l

and 2) to provide a shoulder on the lower side' of the interior of thepipe so as'toiconstituteia valve seat.

A displaceable valve member 46 having a conical valve head surface 46aisfaccommodatedito# gether with a coiled compression,spring,4I..withL inthe lower end portion 26h' ofthe pipebelovv` the constriction thereof. Ahollow plug 48, which may be threadedly engaged inzthexlowermostfenrlf.

portion of the pipe 26, serves as anabutment for. the springy 41. In analternative construction the pipe 26"(Fig.

3) has engaged therewith a tube 49 of somewhat larger diameter, saidtube accommodating the valve member 46, thespring;.-.4.1f.and @111548,whilstthevalveseatais Tpresenteszidoy the inner periphery of thelower..end ,ofzfthe pipe v1:2-6.

In operation the upper and lower portionseof.:

the-cylinder.. I 4' .are completely; filled withia suitable liquidA suchas oil, `which.isealso introduced? so las to partly yfilltheaannularreservoir be-y tween the outside of .thecylinderzaandtheinside of they,tube r,21).` vIf--tl1e motionof.4 theftwo parts of the .vehi'cle'flis;.suc-:hltl:1at1theipistonfiis4 moved. in .-a downward 1 direction irelative -to- Athe cylinder, the piston fzefEects-:seating si. of thel.valve assembly, comprised:bythesspring;steel-.valve disc 28 :i and acomplementary -annularfseating pre-vv sented f by :the ..base'i'21.,whilstfthemvalve i I Bf infthe piston 'f isunseated so sasiftoiallowliquid .to )pass` upwardly throughathegpistonil I; Due-:to thefin-,Ytroduction' of .part of the .pistoni-rod.,- into.v y-the cylinder ithere will be can- ".fexcess'li or` differential amountof oilwhichihastorhe:displacedifrom'the upperl portion of the-zcylinderftll.;'lhisioi-lffowsthrough the :passage @ways @2li :andi-i2 Iu; .through they pine {261.:and jthe Vvalve. tithe-bottom rotti-ierpipe- -2-6 isfunseated.; Such dispaced; liquidzthenrf passes intothe-annularirescrvoir.: Productionzof foam-is substantiallyqsavoide'd:by ndmission'beloww the level in Ysaid reservoir:y

The restriction'ieiect :of ythe massages .fZIiIt :and 2 Iu, `and vof thepipe-Qrand=rthe valve if;assembly;` at the :bottoml thereof :fdependszupon'the size of (Obviously,r if all. stronger spring::isuincludedf`-insrthewvalve assembly:v at thewbottomifnfitherpipei;thefrchar.-v acteristics of the'vvalveandithe restrictionzaeiect uponthe passage-,of-.fliguidwill b'ervariedaccorcb` such ypassages `or:otheit components ingly. The general :characteristicsfoffbothwupfward-.and downwardmovementfzare initiallymbtainedain the ratio :selected.fbetweenfxthe piston rod 4 `and piston crossesectional;4 arrangements`If y movement .between .thesvehicle .parts isesuch l as tocause upward.movement h.of the piston-.LI 60 relative to .the cylinder.,.I.4, such,upward movement will cause .an .unseating of;th'e.valve..as=

sembly comprised'v bythe spring steel 'valve disc 2s and the valve.seatpresentedbytheibase ;21,"

allowing liquid *to Apass from thegreseryoir finto. 65 the "lowerportionfcifthe cyli'n'der *I 4:1. The valve a I6 will, on' the-otherghand;"remain-rseatedf"infthe *piston` and vduetofthereductioninfrvolume i of the space in thel cylinder above ftheipiston;` an excess of liquid willhaga'in'lfbe forced "out-byf way vof.`:the :passages inzithe vi'sylin'cle'r, 'head and willi :be fa cyclical.-:mo ,eintrat-.foty

4 out of the cylinder through the cylinder head and into the reservoir.A* I :'"Onfsmallrrelative movmentiofjthegpiston or cylinder, "fluid:Vcirculatesbetween the' l'cylinder 5 and the reservoir through bleedholes or a metering device; for example, through a. groove (46a) .intheaconicaliface of valvemember 46.

`Itfhas been 'found that in certain circumstances the pressure reliefvalves, I6 and 46 10fare-1proneitoprdduce noise, usually of a highpiston. :Theflowi of...'tl1`e.liquid.can. occur through a, small.orifice,..nr, alternatively, .between ,the .pis-

ton. and.. its. cylinder. Themesistance oferedto thisiioweffectsitherdamping, i. e. curtails. the flutter..

Referring, in.. particular, to Fig.. .4, .the lower end. of the-pistonrodQ I 2..ispaxially bored to provide-alcylinder. I2dWithinwhicha valve member I6 of generally. cylindrical configurationis laxiallyv displaceable. against..the, action. of a small. .coil spring.The.. valve. member I6 is slightly undersize .(Fig. 8) sosthatthe.working fluid is able to pass between it andthecylinder I.2a.and.henceto 4escapeviableed-.hole 412b.v Simi1arly,f-.th'e. valve.. member.dflatthefbottom Vof .the

liquidhd-ischarge passage .isfarranged .to reciprocate as a .pistonwithin the .2 tube ..or cylinder 49, .Workingnuid passingfrom...thempassage .2lil into v,thegreservoir.;thmugh. aperturel49b and -via` 4Uthe bleed .passage-148e .mthe-.plug 48..Communication:betweensthecylinderA9.andthe resl ervoir is.. affordedbyameans of.` Ya rectangular portas showndn dotted lines...

AIn .the .further A.embodiment of .the Ainvention illustrated v,in.Eigs.. 5vv and .6, .a itelescopic, shock absorber :(Fig.: 5)includesaa-.piston-SIJ fixed-.to a

piston rodl I .by.,.screw fthreacL/and .locked in position thereon r bylmeans l.' of- 1 `a spring clipv 1 52. Contained :withinathetpiston isla spherical.v ended, cylindrical..nonreturn .Naive -.-5.3f,.v vwhich.possesses an extension-.pin 54.^of.a reduceddiameter. Thisvalve-.is..guidedv:inf .two axially `bored l.holes in that endaof. ithe.piston-mod ...which -comes within .the

upperfendiofi-pthe.piston 4 .Screwedeinto the lowerendsof' .the-pistonissan l.annularrfscrew 55,I which formsaseatzonto which-thevalvefisiurged under the ...pressures of aspiring-56.. AA :setting fwasher51, of selected.thicknessgzds.finterposedfbetween the send of athenVvpiston-.andithe head `oi the fanmilan-screw..vl .It-willbeappreciatedfthat .according to the thickness of the setting washer, so will thespring load on-fthe'uvalveevary.- Inorder that .the fvalve lwill-.notflutter :orvibrate when subjected-to fluidk pressure, gits '.action.. is--damped regldedzas a piston... The-flowfoffthe :fluid :can occurthrough the .smallihole 258.-v Alternatively, thelilow'can occur .viaasmallwclearance between .the..valve-.and the cylinder (Fig. .9). It is.the ...resistance which is.. .oiered `.to .such Viiow ibm-meansoffithe-fu-id:aitselfgoperating :in the small cylinder in .which theevalve'zitself :can :be

whichxeiects :ithe damping -:onu :the ervalve.. The floweofzthzouglfi-:iahegpistonflitselt fromthezundersidestozthempperside-iis.eeffectedhyir-virtueY: `:175 of .thepressure builuingmpauntuifitaunseats the,

valve 53 and thence flows via the obliquely drilled ports 59'.`

The piston and rod are together displaceable in a pressure cylinder 60,to the lower end of which is fltted a non-return valve body 6| This isof spider formation for location purposes, and possesses three feet.Assembled to it is a spring steel disc 62, slidably mounted on a rivet63 which is secured in an axial bore. The disc is urged onto its seatunder the action of a conical coil spring 64, which thrusts against theunder face of the rivet head. f

The upper end of the pressure cylinder 6|)v is fitted with a cylinderhead 65 having an axially bored hole which serves as a bearingbush forthe piston rod. Contained within a suitable recess in the upper portionof the cylinder head is a lrubber gland 66 having a series ofinternallips, the object of which is to wipe off any fluid ad,- heringto the piston rod. This gland is arranged to sit on asympatheticallyshaped washer 61 which in turn sits on a wavedannularspring 68. 'I'he object of the spring is to cause the gland, b yvirtue of its general external shape, to be compensated for any wearthat takes place on the lips. The gland recess is opened up to the undersurface of the cylinder head by means of an obliquely drilled hole 69 inorder thatv any fluid that is wiped from the piston rod may drain outthrough it.

Fittedto the cylinder head by means of screw thread, and lying in linewith, but outside the cylinder, is a depending tube 10. The bore of thistube is opened up to the interior of the cylinder via an obliquelydrilled passage 1|. Attached to the lower end of the depending tube bysoldering, is a cylindrical valve chamber 12. Contained within thisvalve chambery is a` conically headed valve 13 possessing an extensionpin 14 which guides it inside a hollow screw 15. This valve also is sodesigned that it acts as a small piston working against a spring 16,inside a cylinder, thereby obviating flutter by virtue of the fluiddamping. The valve chamber is cut away on two opposite sides to provideapertures 11 in order that the fluid being displaced from the pressurecylinder as a result of any upward displacement of the piston, may, onunseating the valve, escape into the reservoir formed by the tube 20.The ports formed by the cutaway 11 in the valve chamber also affordcommunication between the discharge pipe and the reservoir. v

All the afore-mentioned parts, can, when assembled, be regarded as theinternal unit.v This is housed within a tube 18 having a bottled form atits lower end and a screw thread at itsupper end. The spidered valvebody serves as a location at the lower end (see Fig. 6) and theperiphery of the cylinder head affords location at the upper end. 'Iheassembled internal unit is urged onto its three feet against the base ofthe tube by the tightening of a screwed nut 19, which is axially boredto allow clearance for the piston rod. The screwed nut and the engagingsurface are so designed that an annular gap of triangular section isapparent between them and the inner periphery of the tube. Trapped orsqueezed within this gap is a rubber sealingr ring 80 the purpose ofwhich is to prevent leakage of fluid from within the shock absorber. I

Attached to the bottom face of the outer tube by welding or brazing is aring forging 8| adapted to connect the tube to a vehicle portion.

Attached to the upper end of the piston rod spring possible.

6... byrscrew thread' is a ring forging 82 :likewise adapted to connectthe pistonv rod to .a vehicle portion. Spot welded onto the periphery ofthis forging is a tube of light section 83, the purpose of which is toprotect the shock absorber from grit and small stones.

In operation, the upper and lower. portions of the cylinder arecompletely 4filled with a suitable fluid preferably oil which is alsointroduced so as to partly ll the annular reservoir between the outsideof the cylinder and the inside of the tube. If the motion of the twoparts of the vehicle is such that the piston is moved downwards relativeto the cylinder, the piston effects seating of the valve at the bottomof the cylinder. At the same time the valve in the piston is unseatedthereby allowing oil to pass upwards through the piston. Due totheintroduction of part of the piston rod into the cylinder there will bean excess or differential amount of'oil which y must be displacedthrough the oblique passage 1|, through the depending tube 10 and thevalve at the bottom of the depending tube is unseated. Such displacedoil then passes vinto the annular reservoir. Production of foam isminimised considerably by admission below the oil level in thereservoir. The restriction effect of the passages and ports and thevalve assembly, depends upon the size of such passages and sizes of thecomponent parts. If a stronger spring is included in the valve assemblyat the bottom of the depending tube, the resistance to flow will varyaccordingly. The general characteristics of both upward and downwardresistances are initially obtained in the ratio selected between thepiston rod and cylinder cross sectional arrangements.

If movement between the vehicle parts is such that the piston is movedupwards relative to the cylinder, the valve at the bottom of thecylinder is unseated, thus allowing oil to pass from the reservoir intothe lower portion of the cylinder. The valve assembly in the piston willon the other hand remain seated and due to the reduction in volume ofthe space above the piston, an excess of oil will again be forced outthrough the oblique passage 1|, through the depending tube and throughthe valve assembly at the bottom thereof. Thus it will be appreciatedthat whichever ldirection of relative movement obtains between thepiston and the cylinder, there will be a cyclical movement of liquidupwardly out of the cylinder, through the depending tube and into thereservoir.

In the event of small relative movement, the oil is allowed to circulatebetween the cylinder and the reservoir through bleed holes or a meteringdevice; for example, through a small groove 84 existing in the sphericalend of the piston valve.

In the plate valve assembly illustrated in Fig. 7, the arrangement is inthe form of a valve body which is fixed by screwing (Fig. 7), to thelower end of a depending tube 9| inside the shock absorber. f

Contained within the valve body 9|) is an annular plate 92 which isurged against a seating face on the valve body by means of an annularwaved spring 93. This spring thrusts against an annular thrust plate 94which ts into the lower end of the valve body.

The complete Valve is held together by rolling over of the lowerperiphery of the valve body, or alternatively by a screwed plug (notshown) which would make adjustable tension on the Oil is directed intothe annular groove 95 in the valve body via the tube 9|. When ammessetheiminumr inve sziisiblcwn nffi'itsj-aseat against tneispringressureaused-by-,ithe-spring ammithe foil dsillovedf-"to--exhaustfintothe external reservoir within tl'x'eshocki'absorber.

The complete valve is positioned] vabout Vhalf Way up E (Fig. "7* centreiline.' C. LL) the' shock absoberfso f-thtt may:serve"av dual purpose byacting-:also'fasa bame ysindtherelciy minimising any tendency forvtheoiltoaerate irisideithe'reservoir,

A1. Alitelescopic hydrulicshock.llosorber ccmcylinder, a :liquidNreservoir` disposed externally to Ssaid fpressureicyliniier, twosimilarly directed nonreturn "valves,` ione? of which :is r a pistonvalve arranged tomeciprocate=withii1 aqcounter bore in thef' connecting,lrod fof'- the-piston aru;ltslf1e-e otherofwwhich'isilocatedatthe^bottom of the pres' surefcylinder,afbl'eedpathffrom*the counter boreL in thejfpis'ton' lrodvtoftlie'interior ofthe pressure piston are :dampedhydraulicallm a l'passageextending ifbetween the --top of the lpressure cylinv der#l andfishetop` of the fliquidireservoir, afdependn ent Lliquid.discharge-pipe*extending :from f said` 302 Number passagetobeneuthwtlieif'levelof liquid-in the reservoir; ande friozrreturnl valveassembly lo- A10' and? further; f "to prevent 1 thew oil- :reservoir-fbeing thrownffb'odily-fup the outer-'cyliriderfby the mo- 7115*pricing, -n==ccmbination;a, .pressure cylinder; af piston .displacea.bleaxiall-yfiwithin -seid :pressure 525.5- cylinderrwherebyoscillations ofitli'e valve 'in the y2. -Atelescopicvihydraulic"shock absorber aslclaimed irl-miamA f1, vwherein .the bleed path at the1=lower=endoff-saidzcylindricalelement. is providejdivwitha; adrlled ,plug closing'vthe endfof-said cylindrical element.

